1. Field of the Invention
The present invention concerns a system and implement for the surveying and mapping of land surfaces by recording unevennesses, and for serving as navigation aid especially in uneven terrain.
2. The Prior Art
The precise recording of surface features causing unevenness of the topography is of importance not only in map-making but, on a smaller scale, in such activities as agriculture and road and airfield construction. In agriculture, unevennesses must be discovered and evened out in order to prevent the undue collection or runoff of rain and irrigation water and to obviate the impairment of the accuracy of farm machinery working, which is unpredictably affected by topographical irregulaties which influence, among other things, the depth of penetration of such implements as cultivators, planting machines, and the like. In airfield runway and road construction, uneven surfaces--caused by uneven foundations--lead to excessive vibrations and rough rides, especially at high speeds, as well as to the accumulation of rain water in puddles.
A great number of implements, relying on a variety of principles, have been devised and are in more or less widespread use. The following are worth mentioning:
Israel Patent Number 38696 is based on the recording of the movements of a damped pendulum. The degree of damping is critical to this type of instrument, since too little will cause excessive swings owing to the influence of inertia, while too much damping will adversely affect the responsiveness of the device. These difficulties have militated against its general introduction.
Also based on a mechanical construction is the so-called inertial platform, which is carried on a vehicle and relies on gyroscopes to maintain a steady position against which deviations from the plane are measured and recorded. One drawback of this system is its extremely high price, another that it is prone to a number of errors that must be taken into account if acceptable results are to be obtained.
Optical principles and techniques are employed in the photogrammetric surveying of the ground, generally from high or low-flying aircraft depending on the quality of the details desired. An important disadvantage of this method is the fact that results are received only after a certain delay, because of the need for processing the photographs taken.
A more modern application of optical methods is a system using laser beams and known under the Trade Name of LASERPLANT. A revolving laser beam creates a stationary plane of monochromatic light against which deviations are measured and recorded by means of a pick-up device locked onto it and carried on an expandable mast mounted on a vehicle, the pick-up being raised and lowered by the mast in accordance with the irregularities encountered. Again, one of the drawbacks is its high price and limited range.
Finally, deviations from the plane can be measured by vehicle-borne ultrasonic sounding equipment. However, the applicability of this system is limited especially by the fact that no plane of reference can be resorted to.
All the methods enumerated, with the exception of the "Laserplan" type of device, have the one common drawback of their inability to refer their measurements to a common plane of reference and will thus give a little or no indication of the overall nature of the terrain surveyed; nor can any of them be used as navigational aids. The "Laserplan" type of device, for its part, is limited in its ranges, both horizontally (distance from the revolving laser beam) and vertically (the heights recordable being circumscribed by the properties of the mast carrying the pick-up device).
The present invention seeks to overcome these drawbacks by presenting a system that is both simple and rugged and produces results that are invariably referred back to a plane of reference, viz. the plane from which the survey initially started.